LOS ANGELES — People whose brains registered a stronger response to sexual cues were likely to have more sexual partners than those whose brains showed a reduced response, a researcher at UCLA’s Semel Institute for Neuroscience and Human Behavior said today.

“These are the first data we know of that link brain responses to actual sexual risk behaviors,” said Nicole Prause, who directs UCLA’s Sexual Psychophysiology and Affective Neuroscience Laboratory.

The 40 men and 22 women — ranging in age from 18 to 40 — participating in the study were asked how many sexual partners they had in the past year. They also were shown 225 images that included non-sexual images and those that ranged from mildly sexual to explicitly sexual.

Researchers used an electroencephalogram, or EEG, to gauge electrical activity in the brains of study participants. The scientists focused on a specific activity in the brain called late positive potential, which reacts to images based on emotional intensity.

“The researchers found that participants who reported having had a higher number of sexual partners in the previous year exhibited similar late positive potential responses to both the graphic and less-graphic sexual images,” according to a UCLA statement.

“Those who reported having had fewer intercourse partners in the previous year ... showed reduced late positive potential responses to the less explicit sexual images and greater response to the more graphic images.”

Said Prause: “If your brain responds very strongly even to very tame pictures of sex, then you seem to be easily sexually excited in the real world, too,”

She said that “if we show very explicit sex pictures, eventually everyone’s brain responds strongly. It is those weaker images, just hinting at sex, that show the difference.”

Prause said the research could aid in the development of strategies for reducing risky sexual behavior, because those with stronger responses to subtle sexual cues may be more motivated to seek sex and more likely to engage in risky behaviors.

The study is published in the current issue of Social Cognitive and Affective Neuroscience.